Processing apparatus and workpiece processing method

ABSTRACT

A workpiece processing method for processing a workpiece using a processing apparatus including a chuck table, a processing unit, a moving mechanism for moving the chuck table and the processing unit relative to each other, and an imaging unit for imaging the workpiece, where the chuck table includes a holding member formed by a transparent body and a supporting member supporting a part of the holding member and connected to an angle control mechanism. The method includes a tape affixing step, a holding step of holding the workpiece by the chuck table via the tape, and an identifying step of imaging the top surface side of the workpiece through the transparent holding member by the imaging unit positioned in a region that is on a lower side of the holding member and is not superimposed on the supporting member, and identifying a region to be processed in the workpiece.

This application is a divisional of application Ser. No. 16/848,344,filed Apr. 14, 2020.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a processing apparatus that processes aworkpiece and a workpiece processing method using the processingapparatus.

Description of the Related Art

A device chip manufacturing process uses a wafer having devices such asintergrated circuits (ICs) or large scale integrations (LSIs) formed ineach of a plurality of regions demarcated by planned dividing lines(streets). A plurality of device chips each having the device areobtained by dividing the wafer along the planned dividing lines.

For dividing the wafer, a cutting apparatus which, for example, includesa chuck table holding the wafer and a processing unit (cutting unit)fitted with an annular cutting blade that cuts the wafer held by thechuck table is used. The wafer is divided into a plurality of devicechips by making the cutting blade rotate and cut into the wafer. Inaddition, a method of dividing the wafer using a laser processingapparatus has recently been used. The laser processing apparatusincludes a chuck table holding the wafer and a processing unit (laserapplying unit) processing the wafer by irradiating the wafer held by thechuck table with a laser beam. For example, there has been proposed amethod which forms a modified region (modified layer) within the waferalong the planned dividing lines by condensing a laser beamtransmissible through the wafer to the inside of the wafer. The regionin which this modified layer is formed is more fragile than otherregions of the wafer. Therefore, when an external force is applied tothe wafer in which the modified layer is formed, the wafer is dividedalong the planned dividing lines with the modified layer as a startingpoint.

When the wafer is to be processed by a processing apparatus typified bythe cutting apparatus and the laser processing apparatus describedabove, the wafer is disposed on the holding surface of the chuck table,and then the position of a region to be processed (processing targetregion) in the wafer is detected by imaging the top surface side of thewafer having the devices formed thereon by an imaging unit such as acamera. Then, on the basis of the detected position of the processingtarget region, alignment which adjusts positional relation between thewafer and the processing unit is performed. Incidentally, depending onthe content of the processing, the processing may be performed in astate in which the top surface side of the wafer is opposed to theholding surface of the chuck table and the undersurface side of thewafer is exposed upward. In this case, the top surface side (lowersurface side) of the wafer is covered by the holding surface of thechuck table. It is therefore difficult to image the top surface side ofthe wafer by the imaging unit. As a result, the processing target regioncannot be detected on the basis of the positions of the devices formedon the top surface side of the wafer or the like.

Accordingly, there has been proposed a processing apparatus which makesit possible to observe the top surface side of the wafer even in a statein which the top surface side of the wafer having the devices formedthereon is covered by the holding surface of the chuck table. Forexample, Japanese Patent Laid-Open No. H06-232255 discloses a cuttingapparatus including an infrared lamp that applies infrared rays thatpass through the wafer. In this cutting apparatus, the infrared raysapplied from the infrared lamp to the undersurface side of the waferpass through the wafer and reach the top surface side of the wafer.Then, a pattern on the top surface side of the wafer is observed bydetecting the infrared rays reflected by the top surface side of thewafer. In addition, Japanese Patent Laid-Open No. 2010-82644 andJapanese Patent Laid-Open No. 2010-87141 disclose a laser processingapparatus including a chuck table formed by a transparent member andimaging means disposed on the lower side of the chuck table. In thislaser processing apparatus, the top surface side of the wafer is imagedfrom the lower side of the wafer through the transparent chuck tableeven in the case where the top surface side of the wafer is covered bythe holding surface of the chuck table.

SUMMARY OF THE INVENTION

The use of the cutting apparatus including the above-described infraredlamp makes it possible to image the top surface side (lower surfaceside) of the wafer and to detect the processing target region on thebasis of the positions of the devices formed on the top surface side ofthe wafer or the like, even when the top surface side of the wafer iscovered by the holding surface of the chuck table. However, the imagingof the top surface side of the wafer is obstructed when a layer nottransmitting infrared rays (metallic layer or the like) is formed on theundersurface side of the wafer or within the wafer, for example.

On the other hand, in the laser processing apparatus including thetransparent chuck table, the imaging means disposed on the lower side ofthe chuck table images the top surface side of the wafer through thechuck table. Therefore, the devices and the like formed on the topsurface side of the wafer can be imaged even when a metallic layer orthe like is formed on the undersurface side of the wafer or within thewafer. However, in this laser processing apparatus, a moving mechanismthat controls the position of the imaging means in a horizontaldirection may be installed, and a rotating mechanism that rotates thechuck table may be installed on a side of the chuck table. It istherefore necessary to secure a region for arranging the movingmechanism and the rotating mechanism within the processing apparatus,resulting in an increased size of the apparatus.

The present invention has been made in view of such problems. It is anobject of the present invention to provide a processing apparatus thatmakes it possible to observe the lower surface side of a workpiece heldby a chuck table and to decrease the size of the apparatus and aworkpiece processing method using the processing apparatus.

In accordance with an aspect of the present invention, there is provideda processing apparatus including a chuck table configured to hold aworkpiece by a holding surface, a processing unit configured to processthe workpiece held by the chuck table; a moving mechanism configured tomove the chuck table and the processing unit relative to each otheralong a direction parallel with the holding surface of the chuck table,an angle control mechanism disposed on the moving mechanism and on alower side of the chuck table, the angle control mechanism controllingan angle of the chuck table; and an imaging unit configured to image theworkpiece held by the chuck table, the chuck table including a holdingmember formed by a transparent body and holding the workpiece and asupporting member supporting a part of the holding member and connectedto the angle control mechanism, the processing apparatus moving thechuck table by the moving mechanism and imaging the workpiece throughthe holding member by the imaging unit in a state in which the imagingunit is positioned in a region that is on a lower side of the holdingmember and is not superimposed on the supporting member.

Incidentally, preferably, the angle control mechanism is a rotatingmechanism that rotates the chuck table. In addition, preferably, thechuck table further includes an outer circumference holding memberconfigured to hold an outer circumferential portion of the holdingmember, and the outer circumference holding member is supported by thesupporting member. Further, preferably, the processing apparatus furtherincludes an upper side imaging unit configured to image the workpieceheld by the chuck table, from an upper side of the holding member.Moreover, preferably, the processing apparatus further includes apositioning member to which a target for performing positioning betweenthe imaging unit and the upper side imaging unit is set, and the targetis imaged by the imaging unit positioned on the lower side of theholding member and the upper side imaging unit positioned on the upperside of the holding member. Furthermore, preferably, the processingapparatus further includes a moving mechanism configured to move theimaging unit along a direction perpendicular to the holding surface ofthe chuck table.

In accordance with another aspect of the present invention, there isprovided a workpiece processing method for processing a workpiece byusing a processing apparatus, the processing apparatus including a chucktable configured to hold the workpiece by a holding surface, aprocessing unit configured to process the workpiece held by the chucktable, a moving mechanism configured to move the chuck table and theprocessing unit relative to each other along a direction parallel withthe holding surface of the chuck table, an angle control mechanismdisposed on the moving mechanism and on a lower side of the chuck table,the angle control mechanism controlling an angle of the chuck table, andan imaging unit configured to image the workpiece held by the chucktable, the chuck table including a holding member formed by atransparent body and holding the workpiece and a supporting membersupporting a part of the holding member and connected to the anglecontrol mechanism, the workpiece processing method including a tapeaffixing step of affixing a tape to a top surface side of the workpiece,a holding step of holding the workpiece by the chuck table via the tapeafter the tape affixing step; an identifying step of, after the holdingstep, imaging the top surface side of the workpiece through the holdingmember by the imaging unit positioned in a region that is on a lowerside of the holding member and is not superimposed on the supportingmember, and identifying a region to be processed in the workpiece, aprocessing step of cutting the workpiece along the region to beprocessed, by the processing unit after the identifying step, adetecting step of, after the processing step, imaging the top surfaceside of the workpiece through the holding member by the imaging unitpositioned in the region that is on the lower side of the holding memberand is not superimposed on the supporting member, and detecting adifference between a position of the region to be processed and aposition of a processing trace formed in the processing step, and aposition correcting step of correcting a position to be processed by theprocessing unit on the basis of the difference between the position ofthe region to be processed and the position of the processing trace.

In accordance with another aspect of the present invention, there isprovided a workpiece processing method for processing a workpiece byusing a processing apparatus, the processing apparatus including a chucktable configured to hold the workpiece by a holding surface, aprocessing unit configured to process the workpiece held by the chucktable, a moving mechanism configured to move the chuck table and theprocessing unit relative to each other along a direction parallel withthe holding surface of the chuck table, an angle control mechanismdisposed on the moving mechanism and on a lower side of the chuck table,the angle control mechanism controlling an angle of the chuck table, anda first imaging unit and a second imaging unit configured to image theworkpiece held by the chuck table, the chuck table including a holdingmember formed by a transparent body and holding the workpiece and asupporting member supporting a part of the holding member and connectedto the angle control mechanism, the workpiece processing methodincluding a holding step of holding the workpiece by the chuck tablesuch that a top surface side of the workpiece is opposed to an uppersurface of the holding member, an identifying step of, after the holdingstep, imaging the top surface side of the workpiece through the holdingmember by the first imaging unit positioned in a region that is on alower side of the holding member and is not superimposed on thesupporting member, and identifying a region to be processed in theworkpiece, a processing step of, after the identifying step, forming aprocessed groove along the region to be processed, on an undersurfaceside of the workpiece by the processing unit, a detecting step of, afterthe processing step, imaging the processed groove by the second imagingunit positioned on an upper side of the holding member, and detecting adifference between a position of the region to be processed and aposition of the processed groove, and a position correcting step ofcorrecting a position to be processed by the processing unit on thebasis of the difference between the position of the region to beprocessed and the position of the processed groove.

The processing apparatus according to one aspect of the presentinvention can image the workpiece through the holding member by theimaging unit in a state in which the imaging unit is positioned in aregion that is on the lower side of the holding member and is notsuperimposed on the supporting member, by moving the chuck table by themoving mechanism. It is thus possible to perform positioning between theimaging unit and the holding member without separately providing amoving mechanism for moving the imaging unit in a horizontal direction.The processing apparatus can therefore be miniaturized. In addition, inthe above-described processing apparatus, the angle control mechanism isdisposed on the lower side of the chuck table. Therefore, theinstallation area of the processing apparatus is reduced as comparedwith a structure in which the angle control mechanism is disposed on aside of the chuck table, for example.

The above and other objects, features and advantages of the presentinvention and the manner of realizing them will become more apparent,and the invention itself will best be understood from a study of thefollowing description and appended claims with reference to the attacheddrawings showing a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view depicting a laser processing apparatus;

FIG. 2A is a perspective view depicting a workpiece;

FIG. 2B is a perspective view depicting the workpiece supported by aframe;

FIG. 3A is a plan view depicting a chuck table;

FIG. 3B is a partially sectional side view depicting the chuck table;

FIG. 4A is a plan view depicting a chuck table;

FIG. 4B is a partially sectional side view depicting the chuck table;

FIG. 5 is a partially sectional side view depicting a chuck table fittedwith a positioning member;

FIG. 6A is a partially sectional side view depicting the workpiece heldby the chuck table;

FIG. 6B is an image diagram depicting an image obtained by an imagingunit;

FIG. 7A is a partially sectional side view depicting the workpiece heldby the chuck table;

FIG. 7B is an image diagram depicting images obtained by imaging units;

FIG. 8A is a plan view depicting an undersurface side of the workpieceimaged by the imaging unit;

FIG. 8B is a bottom view depicting a top surface side of the workpieceimaged by the imaging unit;

FIG. 8C is a bottom view depicting the top surface side of the workpieceprocessed along planned dividing lines;

FIG. 9A is a bottom view depicting the top surface side of the workpiecewith a first outer circumferential region imaged by the imaging unit;and

FIG. 9B is a bottom view depicting the top surface side of the workpiecewith a second outer circumferential region imaged by the imaging unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment according to one aspect of the present invention willhereinafter be described with reference to the accompanying drawings.FIG. 1 is a perspective view depicting a laser processing apparatus 2 asan example of configuration of a processing apparatus according to thepresent embodiment.

The laser processing apparatus 2 includes a base 4 supporting eachconstituent element constituting the laser processing apparatus 2. A topsurface (upper surface) 4 a of the base 4 is formed substantiallyparallel with an X-axis direction (first horizontal direction) and aY-axis direction (second horizontal direction). In addition, in the base4, a supporting structure 6 in a rectangular parallelepipedic shape isdisposed along a Z-axis direction (a vertical direction or anupward-downward direction).

A moving mechanism (moving unit) 8 is provided on the top surface 4 a ofthe base 4. The moving mechanism 8 includes a pair of Y-axis guide rails10 arranged substantially in parallel with the Y-axis direction. AY-axis moving table 12 is mounted on the pair of Y-axis guide rails 10in a state of being slidable along the Y-axis guide rails 10. A nutportion (not depicted) is provided on the undersurface (lower surface)side of the Y-axis moving table 12. A Y-axis ball screw 14 disposedsubstantially in parallel with the pair of Y-axis guide rails 10 isscrewed into the nut portion. In addition, a Y-axis pulse motor 16 iscoupled to one end portion of the Y-axis ball screw 14. When the Y-axisball screw 14 is rotated by the Y-axis pulse motor 16, the Y-axis movingtable 12 moves in the Y-axis direction along the pair of Y-axis guiderails 10.

A pair of X-axis guide rails 18 arranged substantially in parallel withthe X-axis direction is provided on the top surface (upper surface) sideof the Y-axis moving table 12. An X-axis moving table 20 is mounted onthe pair of X-axis guide rails 18 in a state of being slidable along theX-axis guide rails 18. A nut portion (not depicted) is provided on theundersurface (lower surface) side of the X-axis moving table 20. AnX-axis ball screw 22 disposed substantially in parallel with the pair ofX-axis guide rails 18 is screwed into the nut portion. In addition, anX-axis pulse motor 24 is coupled to one end portion of the X-axis ballscrew 22. When the X-axis ball screw 22 is rotated by the X-axis pulsemotor 24, the X-axis moving table 20 moves in the X-axis direction alongthe pair of X-axis guide rails 18.

A chuck table (holding table) 26 for holding a workpiece 11 (see FIG.2A) is disposed on the top surface (upper surface) side of the X-axismoving table 20. The upper surface of the chuck table 26 constitutes aholding surface 26 a holding the workpiece 11. The holding surface 26 ais connected to a suction source (not depicted) via a suction passage(not depicted) formed within the chuck table 26. The workpiece 11 isheld under suction by the chuck table 26 by making a negative pressureof the suction source act on the holding surface 26 a in a state inwhich the workpiece 11 is disposed on the holding surface 26 a of thechuck table 26.

FIG. 2A is a perspective view depicting the workpiece 11. The workpiece11 is, for example, a wafer made of silicon or the like and formed in adisk shape. The workpiece 11 has a top surface 11 a and an undersurface11 b. The workpiece 11 is divided into a plurality of regions by planneddividing lines (streets) 13 arranged in a lattice manner so as tointersect each other. The regions each have a device 15 such as an IC,an LSI, or an LED (Light Emitting Diode) formed on the top surface 11 aside of the regions. Incidentally, the material, shape, structure, size,and the like of the workpiece 11 are not limited. For example, theworkpiece 11 may be a wafer formed of a material such as a semiconductor(GaAs, InP, GaN, SiC, or the like) other than silicon, sapphire, glass,ceramic, resin, or metal and having any shape and size. In addition, thetype, quantity, shape, structure, size, arrangement, and the like of thedevices 15 are not limited either.

In addition, the workpiece 11 may be supported by an annular frame forconvenience in processing and conveyance. FIG. 2B is a perspective viewdepicting the workpiece 11 supported by an annular frame 19. A circulartape 17 having a larger diameter than the workpiece 11 is affixed to thetop surface 11 a side of the workpiece 11. Thus, the top surface 11 aside of the workpiece 11 is covered by the tape 17, and the plurality ofdevices 15 are protected by the tape 17. Incidentally, the material ofthe tape 17 is not limited. The tape 17 is, for example, a flexible filmobtained by forming a rubber-based or acrylic-based adhesive layer (gluelayer) on a base material formed of a resin such as polyolefin,polyvinyl chloride, or polyethylene terephthalate. An outercircumferential portion of the tape 17 is affixed to the annular frame19 having a circular opening 19 a of a larger diameter than theworkpiece 11 in a central portion of the annular frame 19. The workpiece11 is thereby supported by the frame 19 via the tape 17 in a state ofbeing disposed inside the opening 19 a.

As depicted in FIG. 1, an angle control mechanism (angle control unit)28 that controls the angle of the chuck table 26 in a horizontaldirection (XY plane direction) is provided on the lower side of thechuck table 26. The angle control mechanism 28 is provided on the X-axismoving table 20 of the moving mechanism 8. The lower end side of thechuck table 26 is connected to the angle control mechanism 28. The anglecontrol mechanism 28 is, for example, formed by a rotating mechanism(rotating unit) that rotates the chuck table 26. The rotating mechanismhas a rotation driving source such as a motor. The rotating mechanismrotates the chuck table 26 about a rotational axis substantiallyparallel with the Z-axis direction. The angle of the chuck table 26 inthe horizontal direction is thereby controlled.

The moving mechanism 8 controls the positions of the chuck table 26 andthe angle control mechanism 28 in a direction parallel with the holdingsurface 26 a of the chuck table 26 (horizontal direction). Specifically,when the X-axis moving table 20 is moved along the X-axis direction, thechuck table 26 and the angle control mechanism 28 move along the X-axisdirection. In addition, when the Y-axis moving table 12 is moved alongthe Y-axis direction, the chuck table 26 and the angle control mechanism28 move along the Y-axis direction. Incidentally, the moving mechanism 8is provided with an X-axis detecting unit (not depicted) detecting theposition of the X-axis moving table 20 in the X-axis direction and aY-axis detecting unit (not depicted) detecting the position of theY-axis moving table 12 in the Y-axis direction. The X-axis detectingunit and the Y-axis detecting unit identify the position of the chucktable 26 in the horizontal direction.

In addition, the laser processing apparatus 2 includes a columnarsupporting arm 30 that projects forward from the front surface side ofthe supporting structure 6. Disposed at an end portion of the supportingarm 30 is a processing unit (laser irradiating unit) 32 that processesthe workpiece 11 by irradiating the workpiece 11 held by the chuck table26 with a laser beam. The processing unit 32 includes a laser oscillator(not depicted) such as a YAG laser or a YVO₄ laser and a condenser (notdepicted) that condenses the laser beam oscillated from the laseroscillator. Incidentally, the wavelength of the laser beam applied fromthe processing unit 32 is not limited and is set as appropriateaccording to the purpose of laser processing. For example, when theworkpiece 11 is subjected to ablation processing, the wavelength of thelaser beam is set such that at least a part of the laser beam isabsorbed by the workpiece 11. In this case, a laser beam absorbable bythe workpiece 11 is applied. In addition, the condenser condenses thelaser beam oscillated from the laser oscillator to a predeterminedposition of the workpiece 11 held by the chuck table 26.

The workpiece 11 is subjected to laser processing by application of thelaser beam from the processing unit 32 to the chuck table 26 in a statein which the chuck table 26 holds the workpiece 11. Incidentally, themovement and angle of the chuck table 26 at a time of the application ofthe laser beam are controlled according to the shape of a region to beprocessed (processing target region) in the workpiece 11. Specifically,the moving mechanism 8 moves the chuck table 26 and the processing unit32 relative to each other along a direction parallel with the holdingsurface 26 a of the chuck table 26. In addition, the angle controlmechanism 28 adjusts the angle of the chuck table 26 by rotating thechuck table 26, for example. The workpiece 11 is, for example, dividedalong the planned dividing lines 13 by ablation processing using theprocessing unit 32. In this case, a processing trace (cut groove) 11 c(see FIG. 6A) reaching the undersurface 11 b from the top surface 11 ais formed in the workpiece 11 along the planned dividing lines 13. Inaddition, a processed groove 11 d (see FIG. 7A) having a depth less thanthe thickness of the workpiece 11 can also be formed on the undersurface11 b side of the workpiece 11 along the planned dividing lines 13 byablation processing.

In addition, a moving mechanism (moving unit) 34 fixed to the frontsurface side of the supporting structure 6 is provided below thesupporting arm 30. The moving mechanism 34 includes a pair of Z-axisguide rails 36 arranged substantially in parallel with the Z-axisdirection. A tabular Z-axis moving plate 38 is slidably mounted on thepair of Z-axis guide rails 36. A nut portion (not depicted) is providedto a side of the Z-axis moving plate 38 facing the Z-axis guide rails36. A Z-axis ball screw 40 disposed substantially in parallel with thepair of Z-axis guide rails 36 is screwed into the nut portion. A Z-axispulse motor 42 is coupled to one end portion of the Z-axis ball screw40. When the Z-axis ball screw 40 is rotated by the Z-axis pulse motor42, the Z-axis moving plate 38 moves in the Z-axis direction along thepair of Z-axis guide rails 36.

A columnar supporting arm 44 projecting forward from the Z-axis movingplate 38 is fixed to the front surface side of the Z-axis moving plate38. In addition, an imaging unit (a lower side imaging unit or a firstimaging unit) 46 imaging the workpiece 11 held by the chuck table 26,from a lower side, is provided to an upper surface side of an endportion (front end portion) of the supporting arm 44. FIG. 1 depicts anexample in which the imaging unit 46 is formed by a low magnificationcamera 46 a and a high magnification camera 46 b. The imaging unit 46may perform imaging by using one of the low magnification camera 46 aand the high magnification camera 46 b or may perform imaging by usingboth the low magnification camera 46 a and the high magnification camera46 b. Each of the low magnification camera 46 a and the highmagnification camera 46 b is, for example, formed by a visible lightcamera, an infrared camera, or the like. The moving mechanism 34 movesthe imaging unit 46 along a direction perpendicular to the holdingsurface 26 a of the chuck table 26 (Z-axis direction). The height(position in the Z-axis direction) of the imaging unit 46 is therebycontrolled.

In addition, an imaging unit (an upper side imaging unit or a secondimaging unit) 48 imaging the workpiece 11 held by the chuck table 26,from an upper side, is installed at a position adjacent to theprocessing unit 32 on the end portion of the supporting arm 30. Theimaging unit 48 is, for example, formed by a visible light camera, aninfrared camera, or the like. Incidentally, the supporting arm 30 may beconnected to a moving mechanism (not depicted) that moves the supportingarm 30 along the horizontal direction or the vertical direction. In thiscase, the positions of the processing unit 32 and the imaging unit 48are controlled by the moving mechanism.

In addition, the laser processing apparatus 2 includes a control section(control unit) 50 that controls the operation of each constituentelement constituting the laser processing apparatus 2. Each of theconstituent elements (the moving mechanism 8, the chuck table 26, theangle control mechanism 28, the processing unit 32, the moving mechanism34, the imaging unit 46, the imaging unit 48, and the like) of the laserprocessing apparatus 2 is connected to the control section 50, so thatoperation of each of the constituent elements is controlled by thecontrol section 50. The control unit 50 is configured by, for example, acomputer.

The laser processing apparatus 2 images the workpiece 11 by the imagingunit 46 disposed on the lower side of the chuck table 26 and performspositioning between the workpiece 11 and the processing unit 32. Inaddition, the chuck table 26 is configured such that the imaging unit 46disposed on the lower side of the chuck table 26 can image the workpiece11. FIG. 3A is a plan view depicting the chuck table 26. FIG. 3B is apartially sectional side view depicting the chuck table 26.Incidentally, FIG. 3B also depicts the workpiece 11 held by the chucktable 26.

The chuck table 26 includes a disk-shaped holding member 60 that isformed of a transparent body and holds the workpiece 11, and acylindrical supporting member 62 that supports the holding member 60from below. The supporting member 62 projects downward from a centralportion of the holding member 60. The lower end side of the supportingmember 62 is connected to the angle control mechanism 28. Incidentally,the holding member 60 and the supporting member 62 are, for example,concentrically arranged as viewed in plan.

The holding member 60 has an upper surface 60 a and a lower surface 60 bformed substantially in parallel with each other. The upper surface 60 aof the holding member 60 corresponds to the holding surface 26 a of thechuck table 26 (see FIG. 1). The upper end side of the supporting member62 is connected to the lower surface 60 b side of the holding member 60.When the supporting member 62 is rotated by the angle control mechanism28, the holding member 60 rotates about a rotational axis substantiallyparallel with the Z-axis direction. A recessed portion 60 c that iscircular as viewed in plan is formed in a central portion on the uppersurface 60 a side of the holding member 60. A porous member 64 formed ofa porous ceramic or the like is fitted into the recessed portion 60 c.In addition, the recessed portion 60 c is connected to a suction source68 via a suction passage provided within the holding member 60, thesupporting member 62, and the angle control mechanism 28 and a valve 66.

The workpiece 11 is, for example, disposed on the holding member 60 suchthat the top surface 11 a side of the workpiece 11 is opposed to theupper surface 60 a of the holding member 60 and such that theundersurface 11 b side of the workpiece 11 is exposed upward.Incidentally, when the chuck table 26 holds the top surface 11 a side ofthe workpiece 11 having the devices 15 (see FIG. 2A) formed thereon, aprotective member (protecting sheet) formed by a resin or the like maybe affixed to the top surface 11 a side of the workpiece 11. The topsurface 11 a side of the workpiece 11 is thereby covered by theprotective member, so that the devices 15 are protected. When the valve66 is opened in a state in which the workpiece 11 is disposed on theholding member 60, a negative pressure acts on the upper surface 60 aside of the holding member 60 via the porous member 64, so that theworkpiece 11 is held under suction by the chuck table 26. While FIG. 3Aand FIG. 3B depict an example in which the holding member 60 is formedin a circular shape as viewed in plan so as to correspond to the shapeof the workpiece 11, the shape of the holding member 60 can be changedas appropriate according to the shape of the workpiece 11.

Here, the diameter of the supporting member 62 is smaller than thediameter of the holding member 60. A region 70 superimposed on theholding member 60 but not superimposed on the supporting member 62 istherefore formed below the holding member 60. In the chuck table 26depicted in FIG. 3B, the region 70 is formed so as to surround thesupporting member 62 and is superimposed at least on an outercircumferential portion of the workpiece 11. The imaging unit 46 isdisposed in the region 70 by controlling the positions of the chucktable 26 and the angle control mechanism 28 by the moving mechanism 8(see FIG. 1). The imaging unit 46 then images the workpiece 11 throughthe holding member 60. As depicted in FIG. 3B, when the top surface 11 aside of the workpiece 11 is opposed to the upper surface 60 a of theholding member 60, the imaging unit 46 images the top surface 11 a sideof the workpiece 11. When the imaging unit 46 images the workpiece 11, adistance between the imaging unit 46 and the workpiece 11 is adjusted bymoving the imaging unit 46 along the vertical direction by the movingmechanism 34. It is thereby possible to focus the imaging unit 46 andobtain a clear image.

Incidentally, the material of the holding member 60 is selected asappropriate according to the type of the imaging unit 46. In a casewhere the imaging unit 46 is formed by a visible light camera, forexample, the holding member 60 is formed by a member that transmitsvisible light. In addition, in a case where the imaging unit 46 isformed by an infrared camera, the holding member 60 is formed by amember that transmits infrared rays. Specific examples of the materialof the holding member 60 include quartz glass, borosilicate glass,sapphire, calcium fluoride, lithium fluoride, magnesium fluoride, andthe like.

By imaging the workpiece 11 by the imaging unit 46 through the holdingmember 60 from below the holding member 60 as described above, it ispossible to image the top surface 11 a side of the workpiece 11 coveredby the upper surface 60 a of the holding member 60. The top surface 11 aside of the workpiece 11 can therefore be observed even when a metalliclayer or the like is formed on the undersurface 11 b side of theworkpiece 11 or within the workpiece 11, for example.

Incidentally, the upper surface 60 a side of the holding member 60 maybe formed in a pear-skin shape having irregular projections anddepressions. Alternatively, minute grooves coupled to the recessedportion 60 c may be formed on the upper surface 60 a side of the holdingmember 60. In this case, when the workpiece 11 is disposed on theholding member 60, gaps are formed between the workpiece 11 and theupper surface 60 a of the holding member 60, and the negative pressureof the suction source 68 acts on the whole of the top surface 11 a sideof the workpiece 11 via the gaps. The workpiece 11 can thereby be heldunder suction securely by the chuck table 26.

However, the projections and depressions and the grooves described aboveare not necessarily required to be formed on the whole of the uppersurface 60 a side of the holding member 60. That is, the holding member60 may have a region in which the projections and depressions or thegrooves described above are not formed (flat region). This flat regionis, for example, provided in a band shape from the center of the holdingmember 60 to the outer peripheral edge of the holding member 60. Morespecifically, four band-shaped flat regions are provided atsubstantially equal intervals along the circumferential direction of theholding member 60 (cross shape as viewed in plan). When the top surface11 a side of the workpiece 11 is imaged by the imaging unit 46, theimaging unit 46 is positioned so as to be superimposed on the flatregion of the holding member 60. It is thereby possible to preventimaging from being obstructed by the projections and depressions or theminute grooves and to obtain a clear image, when the imaging unit 46images the workpiece 11 through the holding member 60.

Incidentally, the imaging unit 46 cannot be disposed in a region inwhich the supporting member 62 is disposed, and it is difficult for theimaging unit 46 to image a region of the workpiece 11 which region issuperimposed on the supporting member 62. Therefore, in a region of theholding member 60 which region is superimposed on the supporting member62, the flat regions may not be provided but projections and depressionsor grooves may be formed. In this case, the region of the workpiece 11which region is superimposed on the supporting member 62 is surelysucked. For example, the holding member 60 is provided with aband-shaped flat region along a first direction (for example, the X-axisdirection) and a band-shaped flat region along a second direction (forexample, the Y-axis direction) intersecting the first direction suchthat the flat regions intersect each other and are not superimposed onthe supporting member 62.

In addition, when the workpiece 11 is imaged by the imaging unit 46, theimaging unit 46 can be positioned in the region 70 by moving the chucktable 26 by the moving mechanism 8 (see FIG. 1). It is thereforepossible to perform positioning between the imaging unit 46 and theholding member 60 without separately providing a moving mechanism formoving the imaging unit 46 in the horizontal direction. Thus, the laserprocessing apparatus 2 can be miniaturized. Further, in the laserprocessing apparatus 2, as depicted in FIG. 3B, the angle controlmechanism 28 is disposed on the lower side of the chuck table 26 so asto be superimposed on the chuck table 26. Therefore, the installationarea of the laser processing apparatus 2 is reduced as compared with acase where the rotating mechanism rotating the chuck table 26 isdisposed on a side of the chuck table 26, for example.

Incidentally, the structure of the chuck table 26 can be changed asappropriate insofar as the workpiece 11 can be imaged by the imagingunit 46. FIG. 4A is a plan view depicting a chuck table (holding table)80. FIG. 4B is a partially sectional side view depicting the chuck table80. The laser processing apparatus 2 can use the chuck table 80 in placeof the chuck table 26 depicted in FIG. 3A and FIG. 3B. The chuck table80 includes a disk-shaped holding member 82 that is formed by atransparent body and holds the workpiece 11, an outer circumferenceholding member 84 that holds at least an outer circumferential portionof the holding member 82, and a supporting member 90 that supports theouter circumference holding member 84 from a lower side.

The holding member 82 includes an upper surface 82 a, a lower surface 82b, and a recessed portion 82 c formed in a central portion on the uppersurface 82 a side. A porous member 92 is fitted into the recessedportion 82 c. Incidentally, the shape, material, and the like of theholding member 82 are similar to those of the holding member 60 of thechuck table 26 (see FIG. 3A and FIG. 3B). The recessed portion 82 c ofthe holding member 82 is connected to a suction source 96 a via asuction passage formed within the outer circumference holding member 84,the supporting member 90, and the angle control mechanism 28 and a valve94 a.

The outer circumference holding member 84 includes an annular uppermember 86 and an annular lower member 88 formed with substantially thesame diameter as the upper member 86 and disposed on the lower side ofthe upper member 86. Incidentally, the upper member 86 and the lowermember 88 may be formed integrally with each other or may be formedseparately from each other. The upper member 86 has an opening 86 c thatpenetrates the upper member 86 from an upper surface 86 a to a lowersurface 86 b. The opening 86 c is formed in such a size as to be able tohouse the holding member 82 therewithin and is, for example, formed in acircular shape having substantially the same diameter as the holdingmember 82. In addition, the thickness of the upper member 86 is set tobe substantially the same as the thickness of the holding member 82. Thelower member 88 has an opening 88 c that penetrates the lower member 88from an upper surface 88 a to a lower surface 88 b. The diameter of theopening 88 c is set smaller than the diameter of the holding member 82and the diameter of the opening 86 c of the upper member 86. Inaddition, the lower member 88 has a plate-shaped supporting portion 88 dreaching a central portion of the lower member 88 from an outercircumferential portion of the lower member 88. The supporting portion88 d is, for example, formed in a sectorial shape as viewed in plan soas to be decreased in width from the outer circumferential portion tothe central portion of the lower member 88.

The supporting member 90 is connected to the lower surface 88 b side ofthe lower member 88. The supporting member 90 supports at least a partof the outer circumferential portion of the outer circumference holdingmember 84 (lower member 88). For example, an upper surface 90 a of thesupporting member 90 is formed in a sectorial shape so as to correspondto the lower surface of the supporting portion 88 d of the lower member88, and the supporting member 90 supports a sectorial region extendingfrom the center to the outer circumferential portion of the outercircumference holding member 84 (lower member 88). The lower end side ofthe supporting member 90 is connected to the angle control mechanism 28.In addition, the supporting member 90 is formed in a shape decreased inwidth (diameter) downward from the upper surface 90 a side. Further, thesupporting member 90 is formed in a shape increased in thickness (lengthin a height direction) toward a central portion thereof from an outercircumferential portion thereof.

In addition, an annular suction hole 86 d that vertically penetrates theupper member 86 is formed in an outer circumferential portion of theupper member 86 (a region in which the opening 86 c is not formed). Thesuction hole 86 d is connected to a suction source 96 b via a suctionpassage formed within the lower member 88, the supporting member 90, andthe angle control mechanism 28 and a valve 94 b. In addition, aplurality of recessed portions 88 e are formed on the upper surface 88 aside of the supporting portion 88 d of the lower member 88. The recessedportions 88 e are connected to a suction source 96 c via a suctionpassage formed in the lower member 88, the supporting member 90, and theangle control mechanism 28 and a valve 94 c.

When the valve 94 c is opened in a state in which the holding member 82is fitted in the opening 86 c of the upper member 86, the negativepressure of the suction source 96 c acts on the lower surface 82 b sideof the holding member 82. The holding member 82 is thereby held undersuction by the outer circumference holding member 84, in a state inwhich at least the outer circumferential portion of the holding member82 is supported by the upper surface 88 a of the lower member 88. Inaddition, when the supporting member 90 is rotated by the angle controlmechanism 28, the holding member 82 and the outer circumference holdingmember 84 rotate about a rotational axis substantially parallel with theZ-axis direction. Incidentally, when the outer circumference holdingmember 84 holds the holding member 82, the supporting portion 88 d issuperimposed on a part of the holding member 82 and supports the holdingmember 82. In addition, a part of the lower surface 82 b side of theholding member 82 is exposed downward through the opening 88 c of thelower member 88.

The chuck table 80 holds the workpiece 11 supported by the frame 19 (seeFIG. 2B). The workpiece 11 is, for example, disposed on the holdingmember 82 such that the top surface 11 a side (tape 17 side) is opposedto the upper surface 82 a of the holding member 82 and such that theundersurface 11 b side is exposed upward. At this time, the workpiece 11is superimposed on the recessed portion 82 c of the holding member 82with the tape 17 interposed therebetween, and the frame 19 issuperimposed on the suction hole 86 d of the upper member 86 with thetape 17 interposed therebetween. When the valve 94 a and the valve 94 bare opened in this state, the negative pressures of the suction source96 a and the suction source 96 b act on the tape 17. The chuck table 80thereby holds under suction the workpiece 11 and the frame 19 via thetape 17.

Incidentally, a region 98 superimposed on the holding member 82 but notsuperimposed on the supporting member 90 is formed below the holdingmember 82. In addition, the imaging unit 46 is disposed in the region 98by controlling the positions of the chuck table 80 and the angle controlmechanism 28 by the moving mechanism 8 (see FIG. 1). The imaging unit 46then images the workpiece 11 through the opening 88 c of the lowermember 88 and the holding member 82. The imaging unit 46, for example,images the top surface 11 a side of the outer circumferential portion ofthe workpiece 11. Then, the control section 50 (see FIG. 1) performspositioning (alignment) between the workpiece 11 held by the chuck table26 or the chuck table 80 and the processing unit 32, on the basis of animage obtained by the imaging unit 46.

Incidentally, as depicted in FIG. 1, the laser processing apparatus 2includes the imaging unit 48 in addition to the imaging unit 46. Thepositioning between the workpiece 11 and the processing unit 32 can alsobe performed by using both the imaging unit 46 and the imaging unit 48.In a case where the alignment is performed by using the imaging unit 46and the imaging unit 48, the positioning between the imaging unit 46 andthe imaging unit 48 is first performed. The positioning between theimaging unit 46 and the imaging unit 48 is performed by making aposition in the horizontal direction (XY plane direction) of a region tobe imaged by the imaging unit 46 coincide with a position in thehorizontal direction of a region to be imaged by the imaging unit 48. Apositioning member provided with a target (alignment mark) for thepositioning, for example, can be used for the positioning between theimaging unit 46 and the imaging unit 48.

FIG. 5 is a partially sectional side view depicting the chuck table 26to which a positioning member 110 is fitted. The positioning member 110is connected to the chuck table 26 depicted in FIG. 5 via a connectingmember 114. The positioning member 110 is, for example, formed by atransparent body in a rectangular parallelepipedic shape. Thepositioning member 110 is fixed to a side of the holding member 60. Thematerial of the positioning member 110 is, for example, similar to thatof the holding member 60. A target (alignment mark) 112 serving as amark for the positioning between the imaging unit 46 and the imagingunit 48 is set on an upper surface 110 a side of the positioning member110. The target 112 can be imaged by the imaging unit 46 and the imagingunit 48. The target 112, for example, corresponds to a colored region onthe upper surface 110 a side of the positioning member 110.

Incidentally, a method of setting the target 112 is not limited as longas the imaging unit 46 and the imaging unit 48 can image the target 112.For example, the target 112 may be a member constituted of a metal orthe like formed on the upper surface 110 a side of the positioningmember 110 or may be a through hole that penetrates the positioningmember 110 from the upper surface 110 a to a lower surface 110 b of thepositioning member 110. In addition, targets 112 may be set on the uppersurface 110 a side and the lower surface 110 b side of the positioningmember 110 so as to be superimposed on each other.

The target 112 is imaged from a lower side by the imaging unit 46 and isimaged from an upper side by the imaging unit 48. Then, the positioningbetween the imaging unit 46 and the imaging unit 48 is performed suchthat the position of the target 112 displayed in an image obtained bythe imaging unit 46 coincides with the position of the target 112displayed in an image obtained by the imaging unit 48. This positioningis performed by the control section 50 (see FIG. 1) of the laserprocessing apparatus 2, for example. The positioning between the imagingunit 46 and the imaging unit 48 may be performed by adjusting theposition of the imaging unit 48 by the moving mechanism (not depicted)connected to the imaging unit 48 or may be performed by controllingoptical systems of the imaging unit 46 and the imaging unit 48. Inaddition, this positioning may be performed on software. In this case,for example, the coordinates of the image obtained by the imaging unit46 and the coordinates of the image obtained by the imaging unit 48 arecorrected according to an amount of displacement of the position of thetarget 112.

Description will next be made of a specific example of a method ofprocessing the workpiece 11 by using the laser processing apparatus 2.The following description will be made of processing of cutting anddividing the workpiece 11 by the application of a laser beam.

First, the tape 17 (see FIG. 2B) is affixed to the top surface 11 a sideof the workpiece 11 (tape affixing step). Next, the chuck table 26 holdsthe workpiece 11 via the tape 17 (holding step). FIG. 6A is a partiallysectional side view depicting the workpiece 11 held by the chuck table26. In the holding step, the workpiece 11 is disposed on the chuck table26 such that the top surface 11 a side is opposed to the upper surface60 a of the holding member 60 and such that the undersurface 11 b sideis exposed upward. Incidentally, a pattern layer (functional layer) 21including various kinds of functional films (a conductive film, aninsulating film, and the like) constituting a plurality of devices 15(see FIG. 2B) is formed on the top surface 11 a side of the workpiece11. In addition, FIG. 6A depicts the workpiece 11 having a metalliclayer 23 formed on the undersurface 11 b side.

Next, a region to be processed in the workpiece 11 is identified byimaging the top surface 11 a side of the workpiece 11 through theholding member 60 by the imaging unit 46 located in a region that is onthe lower side of the holding member 60 and that is not superimposed onthe supporting member 62 (identifying step). In the identifying step,first, the imaging unit 46 is positioned below the supporting member 62by the moving mechanism 34 (see FIG. 1 and the like). Then, the imagingunit 46 is disposed in a position superimposed on the holding member 60but not superimposed on the supporting member 62 by moving the chucktable 26 and the angle control mechanism 28 in the horizontal directionby the moving mechanism 8 (see FIG. 1). Next, the imaging unit 46 imagesthe top surface 11 a side of the workpiece 11 through the holding member60. An enlarged image of planned dividing lines 13 and devices 15 (seeFIG. 2B), for example, is thereby obtained. The region to be processedby the processing unit 32 (see FIG. 1) in the workpiece 11 is identifiedon the basis of the image. This region is, for example, set along thecenter of the planned dividing line 13.

Next, the processing unit 32 cuts the workpiece 11 along the region tobe processed (processing target region) (processing step). In theprocessing step, first, the length direction of the planned dividingline 13 of the workpiece 11 is aligned with the X-axis direction. Inaddition, positional relation between the processing unit 32 and thechuck table 26 is adjusted so that the laser beam is applied to theprocessing target region of the workpiece 11. Then, the chuck table 26is moved in the X-axis direction while the laser beam is applied fromthe processing unit 32 to the undersurface 11 b side of the workpiece11. The laser beam is thereby applied along the planned dividing line13. Incidentally, laser beam application conditions (position of acondensing point, power, a spot diameter, a repetition frequency, thenumber of times of application, and the like) are set such that theworkpiece 11 is cut along the planned dividing line 13. As a result, aprocessing trace (cut groove) 11 c reaching the top surface 11 a fromthe undersurface 11 b of the workpiece 11 is formed in the workpiece 11.

Next, the imaging unit 46 located in a region that is on the lower sideof the holding member 60 and is not superimposed on the supportingmember 62 images the top surface 11 a side of the workpiece 11 throughthe holding member 60, and a difference between the position of theregion to be processed and the position of the processing trace 11 c isdetected (detecting step). In the detecting step, first, the imagingunit 46 is disposed in a position superimposed on the holding member 60but not superimposed on the supporting member 62 by a procedure similarto the above-described identifying step. Then, the imaging unit 46images the top surface 11 a side of the workpiece 11. FIG. 6B is animage diagram depicting an image 120 obtained by the imaging unit 46.The image 120 depicts devices 15 formed on the top surface 11 a side ofthe workpiece 11 and a linear processing trace 11 c formed by theprocessing unit 32 (see FIG. 1).

Next, the position A₁ of the region to be processed and the position A₂of the processing trace 11 c are detected. For example, a centralposition in the width direction of the planned dividing line 13, thatis, a position at equal distances from the two devices 15 adjacent toeach other, is detected as the position A₁. In addition, for example, acentral position in the width direction of the processing trace 11 c isdetected as the position A₂. Then, a difference ΔA between the positionA₁ of the region to be processed and the position A₂ of the processingtrace 11 c is detected by the control section 50 (see FIG. 1). This ΔAis stored in a storage unit included in the control section 50, ascorrection information for correcting, in a subsequent correcting step,the position of the region to be processed. By this detecting step, anamount of displacement between the position of the region to beprocessed and the position of an actually processed region isidentified.

Next, the position of the workpiece 11 to be processed by the processingunit 32 is corrected on the basis of the difference ΔA between theposition A₁ of the region to be processed and the position A₂ of theprocessing trace 11 c (position correcting step). This positioncorrecting step is, for example, performed after a predetermined numberof processing traces 11 c are formed or before processing of anotherworkpiece 11 is started after processing of one workpiece 11 iscompleted. In the position correcting step, ΔA obtained as thecorrection information in the detecting step is referred to, and thepositions of the chuck table 26 and the processing unit 32 are shiftedby ΔA. A difference between the position of the region to be processedand the position of the actually processed region is thereby reduced.When the processing trace 11 c is then formed along all of the planneddividing lines 13, the workpiece 11 is divided into a plurality ofdevice chips each having a device 15.

Incidentally, the above description has been made of a case where aprocessing position is corrected on the basis of the position of theprocessing trace 11 c produced by cutting the workpiece 11. However, theprocessing position can also be corrected on the basis of the positionof a processed groove 11 d (see FIG. 7A) formed on the undersurface 11 bside of the workpiece 11 to a depth not reaching the top surface 11 a.The following description will be made of a method of correcting theprocessing position on the basis of the processed groove 11 d.

First, the chuck table 26 holds the workpiece 11 (holding step). FIG. 7Ais a partially sectional side view depicting the workpiece 11 held bythe chuck table 26. In the holding step, the workpiece 11 is disposed onthe chuck table 26 such that the top surface 11 a side is opposed to theupper surface 60 a of the holding member 60 and such that theundersurface 11 b side is exposed upward. The above-describedidentifying step is thereafter performed to identify the region to beprocessed in the workpiece 11.

Next, the processing unit 32 (see FIG. 1) forms the processed groove 11d in the workpiece 11 along the region to be processed (processingstep). In the processing step, first, the length direction of theplanned dividing line 13 of the workpiece 11 is aligned with the X-axisdirection. In addition, positional relation between the processing unit32 and the chuck table 26 is adjusted so that the laser beam is appliedto the region to be processed. Thereafter, the chuck table 26 is movedin the X-axis direction while the laser beam is applied from theprocessing unit 32 to the undersurface 11 b side of the workpiece 11.The laser beam is thereby applied along the planned dividing line 13.Incidentally, laser beam application conditions are set such that theprocessed groove 11 d having a depth smaller than the thickness of theworkpiece 11 is formed on the undersurface 11 b side of the workpiece11.

Next, the imaging unit 48 positioned on the upper side of the holdingmember 60 images the processed groove 11 d, and a difference between theposition of the region to be processed and the position of the processedgroove 11 d is detected (detecting step). In the detecting step, theimaging unit 48 images the processed groove 11 d from the undersurface11 b side of the workpiece 11. FIG. 7B is an image diagram depicting animage 122 obtained by the imaging unit 46 and an image 124 obtained bythe imaging unit 48. Incidentally, the image 122 is an image obtained byimaging the top surface 11 a side of the workpiece 11 by the imagingunit 46 in the above-described identifying step. However, the topsurface 11 a side of the workpiece 11 may be imaged by the imaging unit46 again in the detecting step. The image 122 indicates devices 15formed on the top surface 11 a side of the workpiece 11. In addition,the image 124 indicates the processed groove 11 d formed on theundersurface 11 b side (metallic layer 23 side) of the workpiece 11.

Next, the position B₁ of the region to be processed and the position B₂of the processed groove 11 d are detected. For example, a centralposition in the width direction of the planned dividing line 13, thatis, a position at equal distances from the two devices 15 adjacent toeach other, is detected as the position B₁ on the basis of the image122. In addition, for example, a central position in the width directionof the processed groove 11 d is detected as the position B₂ on the basisof the image 124. Then, the control section 50 (see FIG. 1) detects adifference ΔB between the position B₁ of the region to be processed andthe position B₂ of the processed groove 11 d. This ΔB is stored in astorage unit included in the control section 50, as correctioninformation for correcting, in a subsequent correcting step, theposition of the region to be processed.

Next, the position of the workpiece 11 to be processed by the processingunit 32 is corrected on the basis of the difference ΔB between theposition B₁ of the region to be processed and the position B₂ of theprocessed groove 11 d (position correcting step). In the positioncorrecting step, ΔB obtained as the correction information in thedetecting step is referred to, and the positions of the chuck table 26and the processing unit 32 are shifted by ΔB. A difference between theposition of the region to be processed and the actually processedposition can thereby be reduced.

Incidentally, positioning between the workpiece 11 and the processingunit 32 before the performance of the processing of the workpiece 11 canalso be performed by using the imaging unit 46 and the imaging unit 48.The following description will be made of a specific example of thepositioning between the workpiece 11 and the processing unit 32.

First, the imaging unit 48 provided on the upper side of the holdingmember 60 images the undersurface 11 b side (upper surface side) of theworkpiece 11 held by the chuck table 26. FIG. 8A is a plan viewdepicting the undersurface 11 b side of the workpiece 11 imaged by theimaging unit 48. The imaging unit 48, for example, images a plurality ofouter circumferential regions 130 (four outer circumferential regions inFIG. 8A) of the workpiece 11.

When the imaging unit 48 obtains images of the outer circumferentialregions 130 of the workpiece 11, the control section 50 (see FIG. 1)detects the coordinates of an outer peripheral edge (edge portion) ofthe workpiece 11 at three or more positions (for example, fourpositions). The outer peripheral edge of the workpiece 11 is detectedby, for example, subjecting the images obtained by the imaging unit 48to predetermined image processing (edge detection or the like).Thereafter, the control section 50 detects the center coordinates,diameter, and the like of the workpiece 11 on the basis of thecoordinates of the outer peripheral edge of the workpiece 11. The shapeof the workpiece 11 is thereby identified. In addition, whether or notthe workpiece 11 is disposed in a desired position on the chuck table 26is checked on the basis of the center coordinates of the workpiece 11and the coordinates of the outer peripheral edge.

Meanwhile, the imaging unit 46 provided on the lower side of the holdingmember 60 images the top surface 11 a side (lower surface side) of theworkpiece 11 held by the chuck table 26. FIG. 8B is a bottom viewdepicting the top surface 11 a side of the workpiece 11 imaged by theimaging unit 46. Incidentally, targets (alignment marks) 132 serving asmarks at a time of positioning between the workpiece 11 and theprocessing unit 32 (see FIG. 1) are set on the top surface 11 a side ofthe workpiece 11. FIG. 8B depicts, for instance, an example in which apair of targets 132 is set.

For example, the imaging unit 46 images an outer circumferential region134 on the top surface 11 a side of the workpiece 11 from the lower sideof the holding member 60. An image obtained by the imaging unit 46indicates devices 15 and the targets 132 formed on the top surface 11 aside of the workpiece 11. Then, on the basis of the positions of thedevices 15 and the targets 132 indicated in the image, the controlsection 50 (see FIG. 1) adjusts the position and angle of the chucktable 26 and thereby performs positioning between the workpiece 11 andthe processing unit 32. For example, the angle of the chuck table 26 isadjusted such that the pair of targets 132 set on the workpiece 11 isdisposed on one straight line parallel with the X-axis direction (seeFIG. 1). In addition, the position of the chuck table 26 is adjustedsuch that the position of a planned dividing line 13 of the workpiece 11coincides with the application position of the laser beam. The angle ofthe chuck table 26 is controlled by the angle control mechanism 28 (seeFIG. 1 and the like), and the position of the chuck table 26 iscontrolled by the moving mechanism 8 (see FIG. 1). Incidentally, thedimensions of the device 15, the width of the planned dividing lines 13,and the like may be measured on the basis of the image obtained by theimaging unit 46. In this case, intervals of laser application regions orthe like can be set on the basis of the actual dimensions of the devices15 and the actual width of the planned dividing lines 13.

The workpiece 11 is thereafter subjected to predetermined processing byapplication of the laser beam from the processing unit 32 to theundersurface 11 b side of the workpiece 11. FIG. 8C is a bottom viewdepicting the top surface 11 a side of the workpiece 11 processed alongplanned dividing lines 13. The workpiece 11 is, for example, dividedalong the planned dividing lines 13 by the application of the laserbeam.

Incidentally, when the positioning between the workpiece 11 and theprocessing unit 32 is performed, the imaging unit 46 may image aplurality of regions of the workpiece 11. FIG. 9A is a bottom viewdepicting the top surface 11 a side of the workpiece 11 with a firstouter circumferential region 136 a imaged by the imaging unit 46. FIG.9B is a bottom view depicting the top surface 11 a side of the workpiece11 with a second outer circumferential region 136 b imaged by theimaging unit 46.

The imaging unit 46 first images the first outer circumferential region136 a of the workpiece 11. The angle of the workpiece 11 is thenadjusted on the basis of an image of the first outer circumferentialregion 136 a which image is obtained by the imaging unit 46 (see FIG.9A). Here, in a case where the positioning between the workpiece 11 andthe processing unit 32 is performed on the basis of an image of a regionother than the first outer circumferential region 136 a of the workpiece11, the angle control mechanism 28 (see FIG. 1 and the like) rotates thechuck table 26 in the first direction (for example, clockwise) by 90°(see FIG. 9B), and the imaging unit 46 images the second outercircumferential region 136 b of the workpiece 11. An image of the secondouter circumferential region 136 b of the workpiece 11 is therebyobtained. Then, on the basis of the image of the second outercircumferential region 136 b, the position of the chuck table 26 isadjusted, and the positioning between the workpiece 11 and theprocessing unit 32 is thereby performed. After the positioning betweenthe workpiece 11 and the processing unit 32 is completed, the chucktable 26 is rotated by 90° in a second direction (for example,counterclockwise) opposite from the first direction to return the angleof the workpiece 11 to the state depicted in FIG. 9A. The workpiece 11is thereafter processed along the planned dividing lines 13 by beingirradiated with the laser beam (see FIG. 8C).

In addition, even in a case where the processing trace 11 c (see FIG.6A) or the processed groove 11 d (see FIG. 7A) as a detection target isnot formed in a range that can be imaged by the imaging unit 46 or theimaging unit 48 in the above-described detecting step, a desired regionof the workpiece 11 can be disposed on the upper side of the imagingunit 46 by rotating the chuck table 26 as described above. The positionof the processing trace 11 c or the processed groove 11 d can thereby bedetected in any position of the workpiece 11.

As described above, the laser processing apparatus 2 according to thepresent embodiment can image the workpiece 11 through the holding member60 by the imaging unit 46 in a state in which the imaging unit 46 ispositioned in a region that is on the lower side of the holding member60 and is not superimposed on the supporting member 62 by moving thechuck table 26 by the moving mechanism 8. It is thus possible to performpositioning between the imaging unit 46 and the holding member 60without separately providing a moving mechanism for moving the imagingunit 46 in the horizontal direction. The laser processing apparatus 2can therefore be miniaturized. In addition, in the laser processingapparatus 2, the angle control mechanism 28 is disposed on the lowerside of the chuck table 26. Therefore, the installation area of thelaser processing apparatus 2 is reduced as compared with a structure inwhich the angle control mechanism 28 is disposed on a side of the chucktable 26, for example.

Incidentally, while FIG. 1 depicts an example in which one set of theimaging unit 46 is provided in the rear of the moving mechanism 8, thelaser processing apparatus 2 may be provided with two or more sets ofthe imaging unit 46. For example, a moving mechanism 34, a supportingarm 44 disposed along the X-axis direction from the moving mechanism 34,and an imaging unit 46 fixed to the supporting arm 44 may be provided ona side of the moving mechanism 8. A a result, two regions of theworkpiece 11 (for example, the first outer circumferential region 136 adepicted in FIG. 9A and the second outer circumferential region 136 bdepicted in FIG. 9B) can be imaged without the chuck table 26 beingrotated.

In addition, while the above description has been made of the laserprocessing apparatus 2 that processes the workpiece 11 by theapplication of the laser beam, the type of the processing apparatusaccording to the present invention is not limited. For example, theprocessing apparatus according to the present invention may be a cuttingapparatus that cuts the workpiece 11. The cutting apparatus includes achuck table that holds the workpiece 11, and a processing unit (cuttingunit) fitted with an annular cutting blade that cuts the workpiece 11held by the chuck table. The chuck table 26 depicted in FIG. 3A and FIG.3B or the chuck table 80 depicted in FIG. 4A and FIG. 4B can be used asthe chuck table of the cutting apparatus.

In addition, structures, methods, and the like according to theforegoing embodiment can be modified and carried out as appropriatewithout departing from the objective scope of the present invention.

The present invention is not limited to the details of the abovedescribed preferred embodiment. The scope of the invention is defined bythe appended claims and all changes and modifications as fall within theequivalence of the scope of the claims are therefore to be embraced bythe invention.

What is claimed is:
 1. A workpiece processing method for processing aworkpiece by using a processing apparatus, the processing apparatusincluding a chuck table configured to hold the workpiece by a holdingsurface, a processing unit configured to process the workpiece held bythe chuck table, a moving mechanism configured to move the chuck tableand the processing unit relative to each other along a directionparallel with the holding surface of the chuck table, an angle controlmechanism disposed on the moving mechanism and on a lower side of thechuck table, the angle control mechanism controlling an angle of thechuck table, and an imaging unit configured to image the workpiece heldby the chuck table, the chuck table including a holding member formed bya transparent body and holding the workpiece and a supporting membersupporting a part of the holding member and connected to the anglecontrol mechanism, the workpiece processing method comprising: a tapeaffixing step of affixing a tape to a top surface side of the workpiece;a holding step of holding the workpiece by the chuck table via the tapeafter the tape affixing step; an identifying step of, after the holdingstep, imaging the top surface side of the workpiece through the holdingmember by the imaging unit positioned in a region that is on a lowerside of the holding member and is not superimposed on the supportingmember, and identifying a region to be processed in the workpiece, aprocessing step of cutting the workpiece along the region to beprocessed, by the processing unit after the identifying step; adetecting step of, after the processing step, imaging the top surfaceside of the workpiece through the holding member by the imaging unitpositioned in the region that is on the lower side of the holding memberand is not superimposed on the supporting member, and detecting adifference between a position of the region to be processed and aposition of a processing trace formed in the processing step; and aposition correcting step of correcting a position to be processed by theprocessing unit on a basis of the difference between the position of theregion to be processed and the position of the processing trace.
 2. Aworkpiece processing method for processing a workpiece by using aprocessing apparatus, the processing apparatus including a chuck tableconfigured to hold the workpiece by a holding surface, a processing unitconfigured to process the workpiece held by the chuck table, a movingmechanism configured to move the chuck table and the processing unitrelative to each other along a direction parallel with the holdingsurface of the chuck table, an angle control mechanism disposed on themoving mechanism and on a lower side of the chuck table, the anglecontrol mechanism controlling an angle of the chuck table, and a firstimaging unit and a second imaging unit configured to image the workpieceheld by the chuck table, the chuck table including a holding memberformed by a transparent body and holding the workpiece and a supportingmember supporting a part of the holding member and connected to theangle control mechanism, the workpiece processing method comprising: aholding step of holding the workpiece by the chuck table such that a topsurface side of the workpiece is opposed to an upper surface of theholding member; an identifying step of, after the holding step, imagingthe top surface side of the workpiece through the holding member by thefirst imaging unit positioned in a region that is on a lower side of theholding member and is not superimposed on the supporting member, andidentifying a region to be processed in the workpiece; a processing stepof, after the identifying step, forming a processed groove along theregion to be processed, on an undersurface side of the workpiece by theprocessing unit; a detecting step of, after the processing step, imagingthe processed groove by the second imaging unit positioned on an upperside of the holding member, and detecting a difference between aposition of the region to be processed and a position of the processedgroove; and a position correcting step of correcting a position to beprocessed by the processing unit, on a basis of the difference betweenthe position of the region to be processed and the position of theprocessed groove.